Water from the Colorado River Basin is a major water source for residents of the American Southwest, serving nearly 40 million people. In these urban areas, residential usage is one of the major uses of water, with outdoor water usage regularly representing over fifty percent of each household’s total usage. Outdoor usage is often identified as a target for reduction, as many cities using basin water are facing growing water scarcity concerns. This study compiled the water use of over thirty urban areas using Colorado River Basin water and separated the indoor and outdoor water usage using a combination of the minimum method and smart metering data. Results show a large variability in outdoor water usage per capita between cities with different population sizes and locations. Still, there has been an overall downward trend of outdoor water usage in most large urban areas over the past decade. The outdoor water usage total was then examined for trends with explanatory variables (population, climate, water rates). Initial results showed correlations between higher outdoor usage with higher temperatures and lower precipitation. Our future work will include examining the effectiveness of water conservation policies in the river basin and modeling the effect of past changes in policy, climate, population, and water rates. This work can help quantify the amount of outdoor water usage for municipalities within the Colorado River Basin Service area the effects of various water use reduction efforts such as watering restrictions and turfgrass replacement programs.